Buildings account for 72% of the total electricity consumption in the United States. Consumption is expected to rise to 75% by 2025. Regulating solar radiation gain through windows plays a pivotal role in decreasing building energy consumption. This is a challenging research endeavor as window energy efficiency and cost must also be balanced with the demand for large high-transmission windows for architectural aesthetics as well as occupant comfort. “Smart” glass technology uniquely addresses this challenge.
Smart windows regulate building solar radiation gain by switching from a transparent state when sun is desired for natural lighting, heating, and/or comfort to a tinted (or reflective) state during seasons and/or times of day when building heat gain is problematic. There are a number of chromogenic current technologies that achieve this, including suspended particle, liquid crystal, and electro-, thermo-, gaso-, photo-, and photoelectro-chromic. The operation of these technologies may be subdivided as “active” or “passive.” An active device may be controllably actuated and may be programmed by the building occupant. For example, the user may push a button that applies an electrical bias that switches the device state. This is a desirable feature that adds additional expense and complexity due to the need for additional electrical circuitry. Thermogenic and chromogenic layers typically operate passively where solar radiation may induce switching from transparent to tinted due to high energy light (photochromic) or due to a temperature increase in the layer (thermochromic). This results in lower energy consumption than with standard windows, without the added expense of electrical switching found in electrochromic windows but without the feature of dynamic actuation by the user. The smart glass market is relatively young and is projected to be nearly a one billion-dollar annual industry by 2022. Thus, there remains a need for improved smart glass technologies.